The haggle time is not even 10% of time of purchase.
If buyer wanna save time on buying a vehicle, make sure they go in in a non-busy day so that they wont have bottle neck wait at F&I.
Another biggest one is tell sales guy that you will physically bring in the survey (or mail the unfilled out one) to the sales person when the delivery walk through is a shorter version. They usually don't feel comfortable doing shorter/incomplete version because of survey scores.

Complete brand new walk through is about 30 to 45 minutes depends on manufacturers recommendation.
I just want a 5 minute version.

Those 2 will shave about 25% of buying time.